Re: The validity of cladograms (was Re: giant birds)

[chris brochu <cbrochu@fmppr.fmnh.org>]

Tracy Ford wrote:
> 
> The answer is an overwhelming yes!!! In the majority of cases
> cladograms of extant organisms based on morphological characters are
> congruent with those based on morphologicl characters. I have mentioned
> this a couple of times to support my view that cladistics is the best
> method we have for reconstructing the phylogenies of extinct organisms.
> Your message implies that phylogenetic analysis of DNA is somehow
> "different" to that of morphological characters. Molecular characters
> (DNA) can be analysed using exactly he same methods as morphologicl
> characters (i.e. parsimony). Molecular characters can also be analysed
> using a modelling approach (i.e. maximum likelihood), and by a
> clustering approach (neighbour joining). The latter is not usually
> considered reliable enough on its own for evolutionary reconstructions.
> 
> If yes, then why is it in paleontology, 90 % of the time, different authors
> come up with different cladograms? Why isn't there more of a consensus? 

Are they "different" 90 % of the time?  Tom "Captain Clade" Holtz
presented a good poster at SVP this year showing that, statistically,
the "different" theropod trees out there aren't so "different" after all
- certain select groups are bouncing around in different analyses, but
the general pattern is stable and uniform.


chris

-- 
----------------------
Christopher A. Brochu
Department of Geology
Field Museum of Natural History
Roosevelt Road at Lake Shore Drive
Chicago, IL 60605

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